JPH0332914A - Suspension device of vehicle - Google Patents

Abstract

PURPOSE:To avoid the rapid change of car height by making a suspension character controlling means regulate the rapid change of the flow rate of hydraulic fluid to a fluid cylinder based on the upper acceleration working on a car body for a specified time when specified value or less of car height is detected at the time of starting an engine. CONSTITUTION:Fluid cylinders 3 are installed between a car body 1 and the front wheels and rear wheels 2F and 2R, and the liquid pressure chamber 3c of each fluid cylinder 3 is communicated with a gas spring 5. In addition, proportional flow control valves 9 are provided in the fluid channels 10 fluid supplyably connecting each fluid cylinder 3 and hydraulic pump 8 for supplying fluid, the flow control valve 9 controls the flow rate based on the output of a car height displacement sensor 14, upper and lower acceleration sensor 15, and so on by a control unit 17. That is, when specified value or less of car height is detected at the time of starting an engine, each flow control valve 9 is made to regulate the flow rate of the hydraulic fluid to the fluid cylinder 3 not to rapidly change for a specified time just after the start of the engine.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a suspension system for a vehicle, and more particularly to an active suspension system capable of changing suspension characteristics as desired. .

Prior Art A suspension device called a passive suspension is composed of a hydraulic shock absorber and a damper unit made of a spring such as a coil spring.
Although it is possible to change the suspension characteristics to some extent by making the damping force of the device variable, the range is small, and in practice, the suspension characteristics in passive suspension devices have been set uniformly.

On the other hand, in recent years, a fluid cylinder device has been installed between the sprung mass and the unsprung mass, and a displacement detection means for detecting the displacement of the vehicle has been installed to control the supply and discharge of working fluid to the fluid cylinder device. A suspension device called an active suspension has been proposed, which can change suspension characteristics as desired by controlling based on the amount of displacement of the vehicle body detected by a displacement detection means (for example, Japanese Patent Publication No. 59-14365
(Japanese Patent Application Laid-open No. 130418/1983, etc.).

Generally, there are three types of vehicle vibration: bounce, pitch, and roll, and such active suspension systems include a fluid cylinder device for each wheel.
By a predetermined control gain that is set and controlled based on the amount of displacement of the vehicle body detected by displacement detection means such as vehicle height displacement detection means arranged on each suspension, for example, the amount of displacement of the vehicle height at each wheel of the vehicle. In order to improve riding comfort and running stability, the opening degree of the flow control valve of the fluid cylinder device of each wheel is controlled, and the supply and discharge amount of working fluid to each fluid cylinder device, that is, the fluid flow rate, is controlled as described above. The purpose is to control the vibrations of three types of vehicles.

Problems to be Solved by the Invention As described above, the active suspension device adjusts each wheel to improve riding comfort and running stability against three types of vehicle vibrations, depending on the driving condition of the vehicle. In order to control the fluid flow rate of the working fluid to the fluid cylinder device with a predetermined control gain, a suspension characteristic control means is provided that detects the driving state of the vehicle and changes the settings of each control gain. In suspension systems, when a vehicle is stopped or parked for a relatively long period of time with the engine stopped, the fluid pressure in the fluid cylinder system may drop and cause the vehicle body to fall. Immediately thereafter, the suspension characteristic control means sets a control gain to raise the entire vehicle body based on the low vehicle height detected by the vehicle displacement detection means, thereby increasing the actuation to the fluid cylinders for each suspension. The fluid flow rate of the fluid may change rapidly, causing the vehicle body to rise rapidly, which may cause discomfort to the occupants.

OBJECTS OF THE INVENTION The present invention provides a displacement detection means for detecting displacement of the vehicle, which includes a fluid cylinder device for each wheel between the sprung mass and the unsprung mass of the vehicle, and the displacement detection means. an active suspension device comprising: suspension characteristic control means for controlling the amount of supply and discharge of working fluid to the fluid cylinder device so as to cancel the displacement of the vehicle based on the displacement of the vehicle detected by the system; It is an object of the present invention to provide an active suspension device that can prevent a sudden rise of a vehicle body that may occur immediately after starting an engine.

Structure and Function of the Invention An object of the present invention is to provide acceleration detection means for detecting vertical acceleration acting on a vehicle body, and wherein the suspension characteristic control means is configured such that the displacement detection means detects a vehicle height below a predetermined vehicle height when the engine is started. When the vehicle height of the vehicle is detected, the fluid flow rate of the working fluid to the fluid cylinder changes rapidly within a predetermined period of time immediately after starting the engine, based on the upward acceleration of the vehicle body detected by the acceleration detecting means. This is achieved by being configured to suppress the

According to the present invention, when the displacement detection means detects a vehicle height below a predetermined vehicle height at the time of engine startup, the suspension characteristic control means operates the fluid cylinder device so as to quickly raise the vehicle body to a desired vehicle height. While attempting to rapidly raise the vehicle body by rapidly changing the fluid flow rate of the fluid, the fluid cylinder is This suppresses rapid fluctuations in the flow rate of working fluid to the vehicle body, thereby alleviating the rapid rise of the vehicle body. Therefore, in the above-mentioned active suspension system, when the vehicle height at the time of starting the engine is lower than the predetermined vehicle height, the vehicle body rises immediately after the engine starts, and the vehicle body rises relatively slowly. This prevents the vehicle from rising rapidly.

EXAMPLES Hereinafter, examples of the present invention will be described in detail based on the accompanying drawings.

FIG. 1 is an overall schematic diagram of a vehicle including a vehicle suspension device according to an embodiment of the present invention.

Although only the left side of the vehicle body 1 is illustrated in FIG. 1, the right side of the vehicle body 1 is similarly constructed. In Figure 1, vehicle body 1 and left I? A fluid cylinder device 3.3 is provided between the 77 wheels 2Ft and between the vehicle body 1 and the left rear wheel 2RL, respectively. Inside each fluid cylinder device 3, a hydraulic chamber 3C is formed by a piston 3b fitted into a cylinder body 3a. The upper end of the piston rod 3d connected to the piston 3b of each fluid cylinder 3 is connected to the vehicle body 1, and each cylinder main body 3a is
It is connected to the left front wheel 2PL or the left rear wheel 2RL.

The hydraulic chamber 3C of each fluid cylinder device 3 communicates with the gas spring 5 through a communication passage 4, and each gas spring 5 is divided into a gas chamber 5f and a hydraulic chamber 5g by a diaphragm 5e. The pressure chamber 5g communicates with the hydraulic pressure chamber 3c of the fluid cylinder device 3 through the communication passage 4 and the piston 3b of the fluid cylinder device 3.

A fluid passage 10 connecting the hydraulic pump 8 and each fluid cylinder device 3 so as to be able to supply fluid has a flow rate of fluid supplied to the fluid cylinder device 3 and a flow rate of the fluid supplied to the fluid cylinder device 3.
A proportional flow control valve 9 that controls the flow rate of fluid discharged from the
．． 9 are provided respectively.

The hydraulic pump 8 includes a discharge pressure gauge 1 that detects the discharge pressure of fluid.
2 is provided, and a hydraulic chamber 3 of each fluid cylinder device 3 is provided.
A hydraulic pressure sensor 13.13 is provided for detecting the hydraulic pressure in C.

Furthermore, a vehicle height displacement sensor 14.14 is provided which detects the cylinder stroke amount of each fluid cylinder device 3 and detects the vertical displacement of the vehicle body relative to each wheel 2PL, 2RL, that is, the vehicle height displacement. A vertical acceleration sensor 15. detects the vertical acceleration of the wheels 2PL, 2RL, that is, the vertical acceleration of the springs of the wheels 2PL, 2RL.
15.15 is on the approximately horizontal plane of the vehicle, left and right front wheels 2PL
, one above 2FR and one at the center of the left and right rear wheels in the widthwise direction of the vehicle, a total of three sensors are provided, and a steering angle sensor 18 and a vehicle speed sensor 19 are also provided, respectively.

The discharge pressure gauge 12, the hydraulic pressure sensor 13.13, the vehicle height displacement sensor 14.14, the vertical acceleration sensor 15.15.15,
The detection signals of the steering angle sensor 18 and the vehicle speed sensor 19 are input to the control unit 17 which has a CPL' etc. inside, and the control unit 17 calculates the proportional flow rate based on these detection signals according to a predetermined program. The suspension characteristics are variably controlled as desired by controlling the control valve 9.9.

FIG. 2 shows a fluid cylinder device 3.3.
FIG. 3.3 is a circuit diagram of a hydraulic circuit for supplying fluid to or discharging fluid from these.

In FIG. 2, a hydraulic pump 8 is a hydraulic pump 2 for a power steering device driven by a drive source 20.
An accumulator 22 is connected in communication with a discharge pipe 8a which is connected in parallel with the hydraulic pump 21 and discharges fluid from the hydraulic pump 21 to the fluid cylinder device 3.3.3.3.
On the downstream side of the connecting portion of the accumulator 22, it branches into a front wheel side pipe 23F and a rear wheel side pipe 23H. The front wheel side piping 23F branches into a left front wheel side piping 23FL and a right front wheel side piping 23PR on the downstream side of the branching part with the rear wheel side piping 23R, and the left front wheel side piping 23FL and the right front wheel side piping 23FR are, respectively, Fluid cylinder device 3FL for the left front wheel and fluid cylinder device 3FR for the right front wheel
It communicates with the hydraulic pressure chambers 3c, 3c. Similarly, the rear wheel side pipe 23R is connected to the left rear wheel side pipe 23RL on the downstream side of the branching part.
and branches to the right rear wheel side pipe 23RR, and then branches to the left rear wheel side pipe 23RR.
3RL and the right rear wheel side pipe 23RR communicate with the hydraulic chambers 3.c, 3c of the fluid cylinder device 3RL for the left rear wheel and the fluid cylinder device 3RR for the right rear wheel, respectively.

These fluid cylinder devices 3FL, 3FR, 3RL, 3
RR has gas springs 5FL, 5FR, and 5R, respectively.
L and 5RR are connected, each gas spring 5FL.

5FR, 5RL and 5RR are composed of four gas spring units 5a15bs5''%5d,
These gas spring units 5a, 5b, 5c, 5d are
Corresponding fluid cylinder devices 3FL and 3FR, respectively.
13RL and 3RR hydraulic chambers 3c, 3c, 3c, 3c
The communication path 4 that communicates with the two branches has branch communication paths 4a and 4b.

4c and 4d. In addition, each gas spring 5
PL, 5FR, 5RL, 5RR branch communication path 4a%
4b, 4c and 4d each have an orifice 25
a, 25b, 25c, and 25d are provided, and the damping effect of these orifices 25a, 25b, 25c, and 25d and the buffering effect of the gas sealed in the gas chamber 5f of the gas springs 5FL, 5FR15RL, and 5RR act on the damping force applied to the vehicle. Efforts are made to reduce high frequency vibrations.

Of the gas spring units 5a, 5b, 5c, and 5d constituting each gas spring 5FL, 5FR, 5RL, and 5RR, each fluid cylinder device 3FL, 3FR13RL, and 3R
In the communication path 4 between the first gas spring unit) 5a provided at the position closest to the hydraulic pressure chambers 3c, 3c, 3c, 3C of R and the second gas spring unit) 5b adjacent thereto, , the passage area of the communication passage 4 is adjusted by taking an open position in which the communication passage 4 is opened and a closed position in which the passage area is narrowed, and the gas springs 5FL and 5FR15RL.

Switching valve 26 that switches the damping force of 5RR into two stages
is provided. FIG. 2 shows the switching valve 26 in the open position.

An unload relief valve 28 is connected to the discharge pipe 8 a of the hydraulic pump 8 near the upstream side of the connection part of the accumulator 22 .
When the oil discharge pressure measured in step 2 is equal to or higher than a predetermined upper limit value, the position is switched to the open position, and the oil discharged from the hydraulic pump 8 is directly returned to the reserve tank 29, so that the accumulated pressure of the hydraulic pressure in the accumulator 22 reaches a predetermined value. Controlled to hold the value. In this way, oil is supplied to each fluid cylinder device @3 by the accumulator 2 maintained at a predetermined pressure accumulation value.
This is done using soy sauce from step 2. FIG. 2 shows the unload relief valve 28 in the closed position.

Since the hydraulic circuits for the left front wheel, right front wheel, left rear wheel, and right rear wheel are configured in the same way, only the hydraulic circuit for the left front wheel will be explained below, and the rest will be omitted. do.

The proportional flow control valve 9 is a three-way valve, with a closed position where all ports are closed, a supply position where the left front wheel side piping 23F is opened to the hydraulic pressure supply side, and a return piping where the fluid cylinder device 3 of the left front wheel side piping 23F is opened. It is possible to take the third position in front of the discharge position communicating with 32. FIG. 2 shows the proportional flow control valve 9 in the closed position. Further, the proportional flow rate control valve 9 includes pressure compensation valves 9a, 9a.
The pressure compensating valves 9a, 9a allow the proportional flow control valve 9 to be in the supply position or the discharge position.
The hydraulic pressure within the hydraulic pressure chamber 3C of the fluid cylinder device 3 is maintained at a predetermined value.

A pilot pressure-responsive opening/closing valve 33 that can open and close the left front wheel side piping 23FL is provided on the fluid cylinder device 3 side of the proportional flow rate control valve 9. When the solenoid valve 34 that guides the hydraulic pressure of the left front wheel side piping 23FL on the hydraulic pump 8 side of the proportional flow rate control valve 9 is opened, the hydraulic pressure of the solenoid valve 34 is introduced as pilot pressure into the on-off valve 33. When is equal to or greater than a predetermined value, the on-off valve 33 opens the left front wheel side pipe 23FL, allowing the proportional flow rate control valve 9 to control the flow rate of fluid to the fluid cylinder device 3.

Further, a relief valve 35 that opens when the hydraulic pressure in the hydraulic pressure chamber 3C of the fluid cylinder device 3 increases abnormally and returns the fluid in the hydraulic pressure chamber 3C to the return pipe 32, and the accumulator 2
The ignition is connected to the discharge pipe 8a of the hydraulic pump 8 near the downstream side of the 2 connection part, and opens when the ignition is turned off to return the oil stored in the accumulator 22 to the reserve tank 29 and release the high pressure state in the accumulator 22. A hydraulic pump IJ leaf that returns the oil in the hydraulic pump 8 to the reserve tank 29 to lower the oil discharge pressure of the hydraulic pump 8 when the oil discharge pressure of the hydraulic pump 8 increases abnormally. Return accumulator 38 , which is connected to valve 37 and return piping 32 and performs pressure accumulation when fluid is discharged from fluid cylinder device 3 .
38 are provided respectively.

3A and 3B show the control unit 17
2 is a block diagram of a suspension characteristic control device in the vehicle.

In FIGS. 3A and 3B, the suspension characteristic control device provided in the control unit 17 according to the present embodiment includes a vehicle height sensor 14, 14, 14 for each wheel.
and 14 vehicle height displacement signals X p B, XFLSX□,
Based on XIL, the vehicle height displacement signal XFR1XFL% X1lS'Xit is sent to the control system that controls the vehicle height to the target vehicle height.
Vehicle height displacement speed signal YpmSYFLN obtained by differentiating
A control system B suppresses the vehicle height displacement speed based on Yll and YIL, and a control system B suppresses the vehicle height displacement speed based on the vertical acceleration signals G, SG, L, G of the three vertical acceleration sensors 15, 15 and 15. Control system C that aims to reduce vibration and pressure signals P□, P of hydraulic pressure sensors 13.13.13.13 of each wheel
It consists of a control system that calculates the torsion of the vehicle body based on FLN PIIR% PIIL and suppresses it.

Control system A adds the outputs X0 and XFL of the vehicle height sensors 14.14 of the left and right front wheels 2PL and 2FR, and
A bounce component calculation unit 40 that calculates the bounce component of the vehicle by adding the outputs X I II SX RL of the vehicle height sensors 14.14 of the left and right rear wheels 2RL and 2RR, and a vehicle height sensor 14 of the left and right front wheels 2FL and 2PR. .14 output Xpa
, a pitch component calculation unit 41 that calculates the pitch component of the vehicle by subtracting the added value of Xpt, the left and right rear wheels 2RL, and the added value of the output XIRSXRL of the vehicle height sensor 14.14 of 2RR, the left and right front wheels 2FL, 2PR vehicle height sensor 14
．． 14 output XFII, XFL difference xp+ -XFL
and vehicle height sensor 14.1 for left and right rear wheels 2RL and 2RR.
1D output Xii, XIL (7) difference XRII XI
A roll component calculation unit 42 is provided that calculates a roll component of the vehicle by adding L.

Further, the control system A receives the bounce component of the vehicle calculated by the bounce component calculation unit 40 and the target average vehicle height Tn, and controls the flow of fluid to the fluid cylinder device 3 of each wheel in the bounce control based on the gain. The pitch component of the vehicle calculated by the bounce control unit 43 which calculates the supply amount and the pitch component calculation unit 41 is manually input, and based on the gain K P l, the fluid cylinder device 3 of each wheel in pitch control
The roll component and target roll displacement ITm calculated by the pitch control unit 44 and the roll component calculation unit 42 that calculate the amount of fluid supplied to the
A roll control unit 4 calculates the amount of fluid supplied to the fluid cylinder device 3 of each wheel in roll control based on Rl so that the vehicle height corresponds to the target roll displacement amount T.
It is equipped with 5.

In this way, each control amount calculated by the bounce control section 43, the pitch control section 44, and the roll control section 45 has its sign reversed for each wheel, that is, the vehicle height sensor 14.
Detected at 14.14.14 f: Vehicle height displacement signal X P
11 SX P L % X * l SX I L
is reversed so that its sign is opposite, and then
The bounce, pitch, and roll control amounts for each wheel are added, and the flow signals Q, □QPL, , Q, , to the proportional flow control valve 9 of each wheel in the control system A are
, ,QR, , are obtained.

In addition, each vehicle height sensor 14, ■4.14.14, bounce calculation section 40, pitch calculation section 41, and roll calculation section 42
A dead zone device 70.70.70.70 is provided between the vehicle height sensor 14.14.14.14 and the vehicle height displacement signal XPI, X F L %X RI SX R
L is the preset dead zone X□Xll5Xl1
These vehicle height displacement signals
, XPLSX□, and XRL are output to a bounce calculation section 40, a pitch calculation section 41, and a roll calculation section 42.

Control system B receives vehicle height displacement signals XPI, XFL, X□, and XI input from vehicle height sensors 14, 14, and 14.
Differentiate L and use the following formula to obtain the vehicle height displacement speed signal Y□
, YFL, Y,, yll 46.46
．． 46.46.

Y= (X, -X,l)/T Here, x7 is the amount of vehicle height displacement at time t, Xn-1 is the amount of vehicle height displacement at time t-l, and T is the sampling time.

Further, the control system B calculates the vehicle height displacement speed signal Y II L of the left and right rear wheels 2RL and 2RR from the added value of the vehicle height displacement speed signals Y p L − and Y p * of the left and right front wheels 2PL and 2PR. A pitch component calculation unit 47a that calculates the pitch component of the vehicle by subtracting the added value of %Yli, and vehicle height displacement speed signals Y and LSY for the left and right front wheels 2PL and 2FR.
, , the difference Y, -Y, L and the left and right rear wheels 2RL, 2
Difference Yli between the vehicle height displacement speed signal Y, tSY, on the RR side
- YIL to calculate the roll component of the vehicle.

In this way, the pitch component calculated by the pitch component calculation section 47a is manually input to the pitch control section 48, and the gain KP is
2, each proportional flow control valve 9 in pitch control
The flow rate control amount to the roll component calculation unit 4 is calculated.
The pitch component calculated in step 7b is transmitted to the roll control section 49.
The flow rate control amount to each proportional flow rate control valve 9 in roll control is calculated based on the gains KRP2 and K112.

Further, each control amount calculated by the pitch control section 48 and the roll control section 49 has its sign reversed for each wheel, that is, the vehicle height displacement speed calculated by the differentiator 46, 46, 46, 46. Signal Ypm.

Y24, Y11% YIL is reversed so that its sign is opposite, and then the pitch and roll control amounts for each wheel are added, respectively, and the proportional flow rate control valve 9 of each wheel in control system B is Flow rate signal QF12 to
QPL2QIIR2Q is obtained.

The control system C includes a bounce component calculation unit 5 that adds the outputs G P L SG II of the vertical acceleration sensors 15, 15 and 15, and calculates the bounce component of the vehicle.
a and the sum of 172 (GF
Pitch component calculation 151 calculates the pitch component of the vehicle by subtracting the output G of the vertical acceleration sensor 15 provided at the center of the left and right rear wheels in the vehicle width direction from I + GpL) / 2; Output GF of side vertical acceleration sensor 15
The calculation value of the bounce component calculated by the roll component calculation unit 52 and the bounce component calculation unit 50 that calculates the roll component of the vehicle by subtracting the output GFL of the vertical acceleration sensor 15 on the left front wheel side from I is input, Based on the gain Kfi3, the calculated value of the pitch component calculated by the bounce control unit 53 which calculates the control amount of fluid to each proportional flow rate control valve 9 in bounce control and the pitch component calculation unit 51 is input, and the calculated value of the pitch component is inputted, and the calculated value of the pitch component is inputted. Based on this, the pitch control 154 that calculates the control amount of fluid to the proportional flow control valve 9 in pitch control and the pitch component calculation value calculated by the roll component calculation unit 52 are manually operated, and the gain KRP3,
Pitch control unit 5 that calculates the amount of fluid to be controlled to the proportional flow rate control valve 9 for pitch control based on K1113.
4 and a roll control section 55.

In this way, the bounce control section 53, the pitch control section 5
4 and the control calculated by the roll control unit 55, the positive and negative values are reversed for each wheel, and then the bounce and pitch are controlled for each wheel.

and each control amount of the roll are added, and a flow rate signal QFR3Q, L,
Q, , and QIL3 are obtained.

Note that a dead band device 80.80.80 is provided between the vertical acceleration sensor 15.15.15 and the bounce component calculation section 50, pitch component calculation section 51, and roll component calculation section 52, and the vertical acceleration sensor 15.15. 15. Only when the vertical acceleration signal GpaS Gpt, G, output from 15 exceeds the preset dead zone XG, XG, Xc, these vertical acceleration signals G F l %
GPL%Gn is calculated by a bounce component calculation unit 50,
The signal is output to a pitch component calculation section 51 and a roll component calculation section 52.

The control system uses the hydraulic pressure detection signal PpL of the hydraulic pressure sensor 13.13 of the fluid cylinder device 3 of the left and right front wheels 2PL and 2PR.
s PFI is input, and the difference PFI between the hydraulic pressures of the hydraulic pressure chambers 3c and 3c of the fluid cylinder device 3 of the left and right front wheels 2PR12FL
The ratio P between PFL and these added values PP company ten PPL
r” (Ppm PpL)/ (Pyt+Ppt)
, and if the calculated hydraulic pressure ratio P is -t<Pr<ωL with respect to the threshold hydraulic pressure ratio ωL, the calculated hydraulic pressure ratio Pt is output as is, and on the other hand, Pr
When <-ω or Pt >ωL, the front wheel side hydraulic pressure ratio calculating section 60a1 outputs the threshold hydraulic pressure ratio -ωL or ωL, and similarly, the left and right front wheels 2RL, 2R
A hydraulic pressure detection signal pHLSPill is input from the hydraulic pressure sensor 13.13 of the R fluid cylinder device 3, and the left and right front wheels 2
Hydraulic pressure chambers 3c, 3c of fluid cylinder device 3 of PR, 2FL
The difference in hydraulic pressure PIIIL PILL and their addition value P
Ratio of au+Pre P++ = (PitPILL)/(
and a rear wheel side hydraulic pressure ratio calculating section 60b that calculates the ratio P of the rear wheel side hydraulic pressure.

is multiplied by a predetermined value based on the gain ωF, and then subtracted from the ratio P of the hydraulic pressure on the front wheel side. After that, on the front wheel side, the gain ωC is used to multiply by a predetermined value, and the fluid supply control amount to each wheel is
One of the left and right wheels is reversed so that the positive and negative values are opposite, and the flow rate signal Q is sent to each proportional flow control valve 9 in the control system.
,R.

QFL4, Q114, and QRL4 are obtained.

Each control system A, B, C and D obtained as above
The flow signals to each proportional flow control valve 9 in are added for each wheel to obtain final total flow signals QFR, QFL, QllI, and QRL to each proportional flow control valve 9.

Table 1 shows an example of a control gain map used in each of the control systems A, B, C, and D stored in the control unit 17, and seven modes are set depending on the operating state. has been done.

In Table 1, mode ■ is 60 seconds after the engine stops.
The value of each control gain during seconds, mode 2 is the value of each control gain when the ignition switch is on but the vehicle is stopped and the vehicle speed is zero, and mode 3 is the value of each control gain when the ignition switch is on but the vehicle is stopped and the vehicle speed is zero. The value of each control gain in a straight-ahead state where K G s is 0.1 or less, mode 4 is the value of each control gain in a slow turning state where the vehicle's lateral acceleration G exceeds 0.1 and is 0.3 or less. , mode 5 is the value of each control gain in a medium turning state where the vehicle's lateral acceleration G exceeds 0.3 and is 0°5 or less, and mode 6 is the value of each control gain when the vehicle's lateral acceleration G is 0.5 or less. The values of each control gain in a sharp turning state are shown respectively, and in mode 7, when the reverse roll mode is selected by the roll mode four selection switch (not shown), the vehicle's lateral acceleration G,
Indicates the value of the control gain to be selected instead of mode 4 in a slow turning state where is greater than 0.1 and less than 0.3,
When the vehicle speed exceeds 120 km/h, the system automatically switches to Mode 4 even if the reverse roll mode is selected. In Table 1, Q, AX indicate the maximum flow rate control amount supplied to the proportional flow control valve 9 of each wheel, P, IAx indicate the maximum pressure in the hydraulic pressure chamber 3C of the fluid cylinder device 3, It is set so that the fluid does not flow back into the accumulator 22 from the hydraulic pressure chamber 3C of the fluid cylinder device 3, and P, lIM indicates the minimum pressure in the hydraulic pressure chamber 3C of the fluid cylinder device 3, and the fluid The pressure in the hydraulic chamber 3C of the cylinder device 3 decreases excessively,
The gas spring 5 is set so that it will not be fully stretched and damaged; it will not become sharp. In Table 1, each arrow indicates that the control gain is set to the same value as the value indicated by the arrow.

In Table 1, except for mode 7, each control gain is set so that the larger the mode number is, the more suspension control is performed that emphasizes driving stability. Suspension control is performed by setting each control gain to the values shown in Table 1.

In this embodiment, the suspension characteristic control device configured as described above adjusts the gain of the bounce control section 53 in the control system C shown in FIG. 3B to prevent a sudden rise in vehicle height immediately after starting the engine. 3. Pitch control section 54
gain KP3 of the roll control section 55 and gain KRF3 of the roll control section 55
is configured so that it can be corrected upward immediately after starting the engine.

FIG. 4 is a diagram for changing the gains of the bounce control section, pitch control section, and roll control section in the IIJ control system C of the suspension characteristic control S device shown in FIG. 3 within a predetermined time immediately after starting the vehicle. This is a flowchart.

When the vehicle is parked with the engine stopped,
When the ignition switch is turned on and the vehicle is started, the bounce control section 53 in the control system C has a gain of 7Kp.
3. Based on the gain 7Kp3 of the pitch control section 54 and the gain of the roll control section 55, the above-mentioned suspension characteristic control device performs control (St, S2...
36-9〉.

Generally, when the vehicle is parked for a considerable period of time, the vehicle body 1 is lowered due to a drop in the hydraulic pressure in the hydraulic pressure chambers 3c of each fluid cylinder device 3. , total flow signals QF, 5QFLSQ, to raise the vehicle body l.

, Q, and L are determined, and the proportional flow rate control valve 9 supplies fluid to the flow rate cylinder device 3 to raise the vehicle body 1.

At this time, a vehicle height displacement signal X corresponding to the vehicle height displacement of the vehicle body l
FRSXPLSXilffiSXat, that is, the cylinder stroke amount of each fluid cylinder device 3 detected by each vehicle height sensor 14 is a predetermined li! A, for example, in the case of 20 mts or less, the suspension characteristic control device calculates the total flow rate signal Q p * s Q p L N Q * * based on the gains K13, KP3, and KIF3.
and Ql are determined (Sll-14), but when the vehicle height displacement signal detected by at least one vehicle height sensor 14 exceeds a predetermined value A, the above-mentioned gay 7Kp3, K P
3 and KIF3 upward by predetermined values α, β, and γ, [L(315, S2 to 5>), and performs suspension characteristic control (S9). That is, the suspension characteristic control device
The gain in the bounce control B53 is K B s+α, the gain in the pitch control section 54 is KP3+β, and the gain in the roll control section 55 is K I F
! +γ, the control amount of fluid to each proportional flow control valve 9 in bounce control is calculated based on gain Kss+α, and the fluid control amount to each proportional flow control valve 9 in pitch control is calculated based on gain K P 3+β. Also, based on the gain 7Kp3 +γ, calculate the control amount of fluid to each proportional flow control valve 9 in roll control,
Thus, the flow rate signal QF13Q output from the control system C
PL! , Qllll and QIIL3 set to 0
Flow rate signal QpH3, Q, , set in this way
Q, , and QIL are set to further reduce vertical vibration compared to normal driving, and are therefore controls set to control the vehicle height to the target vehicle height when starting the engine. Flow rate signal Q calculated in system A
p**, QFLI% Quit and QIILl
And the upward acceleration that acts on the car body due to this is
The flow rate signals Qli, QPL3, Qo, and Q of the control system C that are to be further reduced than during normal driving are
RL 3 cancel each other out, and the total flow rate signal QP1
, Q, L,' Q, and Q■ are reduced. That is,
Total flow signal QFl to the proportional flow control valve 9 of each wheel
11QFL, Qill and QIIL are 1 during normal driving: Displacement signal to the car XF1% XFLSXl1% Xi
The flow rate of the fluid supplied to the hydraulic pressure chamber 3 of each fluid cylinder device 3 via each proportional flow control valve 9 is set to a smaller value than the total flow rate signal set based on t. It is suppressed compared to when driving.

For this reason, the vehicle body 1 connected to the piston rod 3d of each cylinder device moves slowly upward, thus preventing the vehicle body 1 from rising rapidly immediately after the engine is started.

When the ignition is turned on and a predetermined amount of time has elapsed,
The suspension characteristic control according to the above flowchart is canceled, and from now on, the suspension characteristic control device sets the bounce control section 53 in the control system C to a gain of 7Kp3, the pitch control section 54 to a gain of 7Kp3, and the roll control section 55 to a gain of (2). Suspension characteristic control during normal driving as shown in FIGS. 3A and 3B is performed.

As described above, according to the present embodiment, the suspension characteristic control device corrects each control gain value in the control system C upward for reducing the vertical vibration of the vehicle within a predetermined period of time immediately after the engine starts to increase the total fluid flow. It Q p *, Q
Since F4, Q, and QIL are determined, the fluid flow rate supplied to the hydraulic pressure chamber 3C of the fluid cylinder device 3 is suppressed, and as a result, the hydraulic pressure in the hydraulic chamber 3 of the fluid cylinder device 3 is The pressure is gradually increased. Therefore, the rise of the vehicle body 1 due to the increase in pressure in the hydraulic chamber 3 becomes a relatively slow movement, thus avoiding a rapid rise of the vehicle body 1 immediately after the vehicle body 1 is started.

The present invention is not limited to the above-mentioned examples, but various modifications can be made within the scope of the invention described in the claims, and these are also included within the scope of the present invention. Needless to say.

Effects of the Invention According to the present invention, each wheel has a fluid cylinder device between the sprung weight and the unsprung weight of the vehicle, and a displacement detection means for detecting the displacement of the vehicle; an active suspension device comprising: suspension characteristic control means for controlling the amount of supply and discharge of working fluid to the fluid cylinder device so as to cancel the displacement of the vehicle based on the displacement of the vehicle detected by the detection means; Accordingly, it is possible to provide an active suspension device that can prevent a sudden rise of the vehicle body that may occur immediately after starting the engine.

[Brief explanation of drawings]

FIG. 1 is an overall schematic diagram of a vehicle including a vehicle suspension device according to an embodiment of the present invention. FIG. 2 is a circuit diagram of a hydraulic circuit that supplies fluid from a hydraulic pump to a fluid cylinder device or discharges fluid therefrom. Figures 3A and 3B are block diagrams of the suspension characteristic control device within the control unit. FIG. 4 is a flowchart for changing the gains of the bounce control section, pitch control section, and roll control section in the control system C of the suspension characteristic control device shown in FIG. 3 within a predetermined time immediately after starting the vehicle. be. l...Vehicle body, 2PL...Left front wheel, 2PR...Left rear wheel,
2RL...right front wheel, 2RR...right front wheel, 3
...Fluid cylinder device, 3FL...Fluid cylinder device for left front wheel, 3FR...
・Fluid cylinder device for right front wheel, 3RL...Fluid cylinder device for left rear wheel, 3RR...Fluid cylinder device for right rear wheel, 3a...Cylinder body, 3b...Piston, 3C・... Hydraulic pressure chamber, 3d... Piston rod, 4... Communication path, 4a, 4b, 4c, 4d-branch communication path, 5... Gas spring, 5FL... Gas spring for left front wheel, 5FR ...Gas spring for right front wheel, 5RL...Gas spring for left rear wheel, 5RR...Gas spring for right rear wheel, 5a, 5b, 5c, 5d-...Gas spring unit, 5e
...Diaphragm, 5f...Gas chamber of gas spring, 5g...Hydraulic pressure chamber of gas spring, 8...Hydraulic pump, 8a...Discharge pipe, 9...
...Proportional flow control valve, 9a...Pressure compensation valve, 10...Fluid passage, 12'...Discharge pressure needle,
13... Hydraulic pressure sensor, 14... Vehicle height displacement sensor, 5... Vertical acceleration sensor, 7... Control unit, 8... Rudder angle sensor, 19... Vehicle speed sensor, 0
... Drive source, l... Hydraulic pump for power steering device, 2...
・Accumulator, 3F...Front wheel side piping, 23R...Rear wheel side piping, 3
FL...Left front wheel side piping, 3FR...Right front wheel side piping, 3RL...Left rear wheel side piping, 3RR...Right rear wheel side piping, 5a, 25b, 25c, 25d...Orifice, 6.
...Switching valve, 8...Unload relief valve, 9...Reserve tank, 3...Opening/closing valve, 34...Solenoid valve, 5...
・Relief valve, 6...Ignition key chain valve, 7...Hydraulic pump relief valve, 8...Return accumulator, 40...Bounce component calculation section, 41...Pitch component calculation section , 42... Roll line segment calculation section, 43... Bounce control section, 44... Pitch control section, 45... Roll #J? #B section, 46... Differentiator, 47a... Pitch component calculation unit, 47b... Roll component calculation unit, 48... Pitch control unit, 49... Roll control unit, 50... Bounce Component calculation unit, 51... Pitch component calculation unit, 52... Roll line segment calculation unit, 53... Bounce control unit, 54... Pitch control unit, 55... Roll control unit, 60... - Warb control section, 60a... Front wheel side hydraulic pressure ratio calculation section, 60b... Rear wheel side hydraulic pressure ratio calculation section.

Claims (1)

[Claims] For each wheel, a fluid cylinder device is provided between the sprung mass and the unsprung mass of the vehicle, and displacement detection means detects the displacement of the vehicle, and the displacement detection means An active suspension device comprising: suspension characteristic control means for controlling the amount of supply and discharge of working fluid to the fluid cylinder device so as to cancel the displacement of the vehicle based on the detected displacement of the vehicle, comprising: The suspension characteristic control means includes an acceleration detection means for detecting an acceleration in the vertical direction acting on the vehicle, and the suspension characteristic control means is configured to cause the displacement detection means to detect a vehicle height that is less than or equal to a predetermined vehicle height at the time of starting the engine. A suspension system for a vehicle, characterized in that the fluid flow rate of the working fluid to the fluid cylinder is suppressed from changing rapidly within a predetermined time period immediately after the engine starts, based on the detected upward acceleration of the vehicle body. .